Question: What combustible gas with the highest IDLH exists in humans?
Paraphrase: Name the combustible gas that has the highest IDLH existing in humans
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q21073026 . ?ent wdt:P2129 ?obj . ?ent wdt:P703 wd:Q15978631 } ORDER BY DESC(?obj)LIMIT 5